Is one who says that the children of idolaters are disbelievers in a metaphorical sense, and not in a real sense, sinful, according to Ibn al-Qayyim's statement that they are idolaters, following their parents in worldly rulings?

Scholars have differed regarding the ruling on the children of polytheists in the afterlife, and the correct view is that they will be tested. As for this world, they follow their parents in rulings, so they are not washed, prayed over, or buried in Muslim cemeteries, because they are considered disbelievers legally, not in reality, for the original state of every newborn is to be born upon fitra (natural disposition). The four Imams have agreed that if a child is captured alone, separated from his parents, he is ruled to be a Muslim because the guardianship of his parents over him is severed. A Muslim should busy himself with his own affairs and what concerns him regarding his religion, rather than extensively delving into matters of dispute.